A gene is a biological unit of heredity and simplified codes for the manufacture of one protein. In some cases these genes are defect and hold wrong information leading to a lack of synthesis or vice versa. In this case gene therapy tries to repair the defect gene. But if it’s possible to increase e.g. muscle proteins, an abuse should be taken into account.

Consequently the capability to misuse gene therapy in sports induced the World Anti-Doping Agency (WADA) to put gene doping on the Prohibited List. It is defined as:
“the non-therapeutic use of cells, genes, genetic elements, or of the modulation of gene expression, having the capacity to enhance athletic performance" (WADA, 2008).

Nevertheless, it isn’t as easy as it seems to manipulate these genes. In the context of physical activity several genes hold the information for endurance enhancing or muscle mass increasing proteins. There is no single “sports” gene!

There are four interesting endurance genes:

• erythropoietin (EPO) stimulating erythropoiesis
• peroxisome proliferator-activated receptor (PPAR ) encoding enzymes of fatty acid oxidation
• hypoxia-inducible factors (HIF) for changes in available oxygen
• angiotensine converting enzyme (ACE) being a vasoconstrictor or vasodilatator
  
  

There are three interesting muscle genes:  

• mechano growth factor (MGF), insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein (IGFBP) for the control of muscle growth
• growth hormone (GH) for the control of muscle mass
• myostatin/growth differentiation factor (gdf-8) or transforming growth factor-b (tgf-b) as a negative muscle growth regulator